The coordinated multiple input multiple output (MIMO) technology, also called the coordinated multiple point transmission and reception (COMP) technology, uses coordinated transmission of transmit antennas in a plurality of cells to improve the capacity and the transmission reliability of wireless links at the cell edge, which may effectively solve the problem of cell edge interference.
In wireless communications, if a plurality of antennas are used at the sending end (eNB), the method of space multiplexing may be used to improve the transmission rate, that is, different data are transmitted at different antenna positions on the same time-frequency resource of the sending end, and a plurality of antennas are also used at the receiving end (user equipment). In general, the MIMO has two transmission forms, one is single user-MIMO (SU-MIMO), which allocates resources of all the antennas to the same user in the case of a single user; and the other one is multi user-MIMO (MU-MIMO), which allocates resources of different antenna spaces to different users in the case of multiple users and realizes services for a plurality of uses through space division at the same time and on the same carrier, and the average throughput within cells may be improved through the MU-MIMO transmission form.
Specifically, the SU-MIMO refers to that one user equipment occupies physical resources allocated to the user equipment alone in a transmission interval. The MU-MIMO refers to that one user equipment and at least one other user equipment share the physical resources allocated to the user equipment in a transmission interval. The one user equipment and other user equipment share the same physical resource (including a time-frequency resource) by way of space division multiple address or space division multiplexing.
The 3rd generation partnership project (3GPP) R8/R9/R10 and subsequent versions of networks use flat network architectures; as shown in FIG. 1, evolved Node B (eNB) is the main body of a wireless network, and an entire access network is wholly composed of eNBs. The eNBs may have a logical or physical connection there between according to requirements, and the bottom layers of the eNBs use Internet protocol (IP) transmission there between and are logically connected to each other through X2 interface, and such a design is mainly used for supporting the mobility of UE in the entire network and guaranteeing seamless switching of uses; in addition, the X2 interface is also responsible for load and interference management. Each eNB is connected to a system architecture evolution (SAE) core network, that is, an evolved packet core (EPC) network, through S1 interface.
Series standards R8/R9/R10 of long term evolution (LTE) define UE specific reference signals, wherein the specific reference signals are mainly used for transmission modes 7, 8 and 9, and the specific reference signals are only embedded in resources of the UE to which the high speed physical downlink shared channel (PDSCH) is mapped. The UE specific reference signals are used, and these reference signals may perform channel estimation on corresponding PDSCH resource blocks so as to demodulate data. Therefore, the UE specific reference signals are regarded as using independent antenna ports and having special channel response from the eNodeB to the UE. This kind of reference signals carry UE information and may only be sent on a frequency band occupied by the data of the UE; therefore, orthogonal frequency division multiplexing (OFDM) symbols occupied by the control channel does not need to be covered in time domain.
A typical usage of the UE specific reference signals is transmitting the data to specific UE through beamforming. For example, not by using a separate physical antenna to transmit cell reference signal (CRS), the eNodeB may use a correlation matrix of a physical antenna unit to generate narrow beams in a specific UE direction. This kind of beams have specific signal response between the eNodeB and the UE, and UE specific reference signals are needed to be used to perform coherent demodulation on beam data. Actually, channel response carried by the UE specific reference signals may be intuitively interpreted as a channel matrix weighted a precoding weight.
One important aspect for limiting the performance of system throughputs in a cellular network is inter-cell interference especially that of cell edge users. Coordinated multiple point transmission and reception (COMP) may coordinate the scheduling and transmission of different cells, effectively deal with interference from adjacent cells, and significantly increase data rate of the cell edge users. In order to realize the coordinated multiple point transmission and reception (COMP), communications are needed to be performed between adjacent cells. If the adjacent cells are managed by the same eNodeB, then the coordinated multiple point transmission and reception does not need standardized signaling. However, in the adjacent cells controlled by different eNBs, the standardized signaling is very important, especially for a multi-vendor network.
In relevant art, as regards the method of the coordinated multiple point transmission and reception in the R11 standard, according to the conclusion of the R10 standard, channel measurement of a down link may be performed based on a CSI-RS, and data reception and demodulation of a downlink transmission link may be performed based on a UE specific RS. However, in a cooperation set, the UE specific reference signals generated by different eNBs using parameters determined thereby have the problem of mutual interference.